Wireless local area networks (“WLANs”) providing broadband wireless connectivity have become tremendously successful in the business and consumer marketplaces. Traditionally, the principal application for WLANs has been providing data connectivity (e.g., web browsing and email) to portable/mobile devices. However, the last few years have demonstrated a growing interest in using WLANs to support voice and video applications (e.g., Voice-over-IP (“VoIP”) telephony, streaming video, and streaming audio).
Since power consumption is often an important constraint on the operability and desirability of portable/mobile devices, implementing VoIP or streaming audio/video in a power saving conscious manner is important. The 802.11 standard (IEEE-802.11, 1999 Ed. (ISO/IEC 8802-11:1999)) defines a legacy Power Save (“PS”) mode of operation. However, the legacy PS mode of operation, which uses a regularly scheduled beacon and polling mechanism, is not well suited for VoIP and streaming audio/video applications where traffic load is very high. Accordingly, the 802.11e standard (IEEE Std. 802.11e/D13.0, January 2005 (Draft Amendment to IEEE Std. 802.11, 1999)) introduced a different delivery mechanism, known as Unscheduled Automatic Power Save Delivery (“UAPSD”), which is also extended by the Wi-Fi Alliance (“WFA”) as part of the Wi-Fi Multimedia (“WMM”) including APSD Specification. The UAPSD delivery mechanism is implemented with trigger and delivery mechanisms. Due to its unscheduled nature, UAPSD is better suited to manage the periodic traffic characteristics typical of VoIP and streaming audio/video applications.
Even UAPSD alone may provide unsatisfactory performance for VoIP and streaming audio/video applications over WLANs, if UAPSD parameters are not appropriately selected for the anticipated traffic. Accordingly, the WMM including APSD Specification (WFA, Version X.X) defines an Admission Control Mechanism (“ACM”) for negotiating UAPSD parameters in advance of anticipated traffic. ACM must be supported by applications on both sides of the wireless link between the wireless client station (“STA”) and the wireless access point (“AP”). To configure the UAPSD parameters to optimize the delivery mechanism for the VoIP traffic, the STA and the AP exchange TSPEC frames (e.g., ADDTS and DELTS) to setup and tear down UAPSD parameters. However, the WMM including APSD Specification defines ACM as optional. Accordingly, if either the STA or the AP does not support ACM, the explicit traffic reservation mechanism cannot be used and default UAPSD parameters may be unsuitably selected for future traffic conditions.